The order things would run would I guess be down to windows and may or may not have to do with which was installed first, but it is a bit like black magic as there doesn't appear to be any reasoning in it.
Blocking the port in OA would be the same as using decombobulator, since avast is getting in first it would alert before the OA block (or decombobulator) got a look in.
@ Mark2234
If you have avast 4.8 I would suggest now would be a good time to update to avast 5.0, if you already have avast 5.0 then, all I can suggest is that you leave OA installed and do a clean reinstall of avast:
This assumes you are using the free version of avast - Download the latest version of avast, 5.0.594
http://www.avast.com/free-antivirus-download and save it to your HDD, somewhere you can find it again (if you didn't save your last download). Use that when you reinstall.
- Download the avast! Uninstall Utility, aswClear5.exe
find it here and save it to your HDD (it has uninstall tools for both 4.8 and 5.0).
- 1. Now uninstall (using add remove programs, if you can't do that start from the next step), reboot.
- 2. run the avast! Uninstall Utility from safe mode, first for 4.8 if previously installed and then for 5.0, once complete reboot into normal mode.
- 3. install the latest version, reboot.